And on your article about Wawrinka, I don't see his heelpad near bevil 7. It seems on your photo it's on bevil 8, just like a normal E bh grip.
Oops. Thanks for the catch. I revised the article to say "bevel 8".
But I think it's somewhat important to note the index finger is not touching the middle finger for most pros. your 'mountain bike' phrase sounds like the index is touching the middle finger, which I wouldn't recommend.
I partly agree, partly disagree.
From what I've seen, most pros have their index finger
tip touching the middle finger, but with a slight gap forming between the two with the index either bowing upward or outward. Typically, this is combined with the index tip pressing up against the thumb.
I think the extent of this finger separation depends on:
1. How far down the heel pad is from the index knuckle
2. whether they are forming a loop with their index and thumb, or if they keep their thumbs outside,
3. how they "feel" the handle to make sure they have the right grip.
Anyway, I think pretty much every pro avoid significant lateral separation between the fingers. A big gap between the fingers is a sign the heel pad isn't far down enough.
^^^ I would argue that this slight gap by Almagro happens mainly because his finger is pressed up against his thumb (forming a loop), which prevents the index finger from fully closing on the handle. He may also be doing this so he can feel bevel 4 with his finger tip.
^^^ same with Stan.
Whatever the cause, these gaps are
tiny compared to what I see some coaches promote.
What happens when we move the thumb out of the way?
^^^ once the thumb is out of the way, the index finger can close down fully. Note how Kuerten's thumb is to the side of his fingers, not underneath.
^^^ same with Pete.
Overall, I think the absence of a gap isn't an immediate warning sign. However, a big gap between the fingers is likely a big problem.